1. Field of the Invention
The present invention relates to a magnetoresistive effect element which produces a high level of output to an outside magnetic field in response to a change in a magnetoresistance. The present invention also relates to a magnetoresistance effect type head including the element suitable for high-density magnetic recording and reproduction, and a magnetic recording apparatus such as a hard disk drive including the head, and methods for fabricating the element, the head, and the apparatus.
2. Description of the Related Art
Recently, hard disk drives (HDD) have been rapidly developed to have more high density capability, and significant advances have been made in reproduction magnetic heads for reading magnetization recorded on such a medium. Among other things, a spin valve which is a magnetoresistance effect element (hereinafter referred to as an MR element) utilizing a giant magnetoresistance effect has been thought to increase the sensitivity of current magnetoresistance effect type heads (hereinafter referred to as an MR head) and is being vigorously studied.
The spin valve includes a non-magnetic layer and two ferromagnetic layers. The non-magnetic layer is sandwiched between the two ferromagnetic layers. The magnetization direction of one of the ferromagnetic layers (pinned layer) is pinned by an exchange bias magnetic field of a pinning layer (the ferromagnetic layer and the pinning layer are referred to collectively as an exchange coupling layer). The magnetization direction of the other ferromagnetic layer (free layer) is allowed to move relatively freely in response to an external magnetic field. The electric resistance of the spin valve is changed according to the angle between the magnetization directions of the pinned layer and the free layer.
Journal of Magnetism and Magnetic Materials 93, p. 101, 1991 discloses a spin valve which includes magnetic layers made of Nixe2x80x94Fe, a non-magnetic layer made of Cu, and a pinning layer made of Fexe2x80x94Mn. This spin valve has a magnetoresistance change rate (hereinafter referred to as an MR ratio) of approximately 2%. When the pinning layer is made of Fexe2x80x94Mn, the MR ratio is small and the blocking temperature (temperature at which a magnetization pinning effect of the pinning layer on the pinned layer vanishes) is not sufficiently high. In addition, Fexe2x80x94Mn has less corrosion resistance. Therefore, other spin valves have been proposed which include a pinning layer made of a variety of material. Among other things, Ptxe2x80x94Mn has good corrosion-resistance and thermal stability. A pinning layer made of an oxide such as NiO and xcex1-Fe2O3 allows the spin valve to have a very high MR ratio of 15% or more.
However, the spin valve including an NiO pinning layer does not have a sufficiently high blocking temperature, so that the NiO spin valve has less thermal stability.
The xcex1-Fe2O3 spin valve has disadvantage such that a pinning effect on the metal magnetic layer is weak. Particularly, when the spin valve has a dual spin valve structure or when a structure such that the xcex1-Fe2O3 layer is provided on the pinned layer, such disadvantage is significant in the xcex1-Fe2O3 layer. The Ptxe2x80x94Mn spin valve has excellent thermal stability, but does not have as high a MR ratio as the NiO or xcex1-Fe2O3 spin valve. Therefore, the thermal stability as exhibited by Ptxe2x80x94Mn and the large MR ratio is exhibited by NiO or xcex1-Fe2O3 have not been achieved in one element.
Moreover, a small total thickness of the metal layers and a higher MR ratio are required for the magnetoresistance effect element.
According to one aspect of the present invention, a magnetoresistance effect element includes a free layer, in which a magnetization direction thereof is easily rotated in response to an external magnetic field; a first non-magnetic layer; and a first pinned layer provided on a side opposite to the free layer of the first non-magnetic layer, in which a magnetization direction of the first pinned layer is not easily rotated in response to the external magnetic field. At least one of the first pinned layer and the free layer includes a first metal magnetic film contacting the first non-magnetic layer, and a first oxide magnetic film.
In one embodiment of this invention, the first pinned layer includes the first metal magnetic film and the first oxide magnetic film.
In one embodiment of this invention, the magnetoresistance effect element further includes a second non-magnetic layer provided on a side opposite to the first non-magnetic layer of the free layer; and a second pinned layer provided on a side opposite to the free layer of the second non-magnetic layer, in which a magnetization direction of the second pinned layer is not easily rotated in response to the external magnetic field.
In one embodiment of this invention, the free layer includes the first metal magnetic film and the first oxide magnetic film.
In one embodiment of this invention, a magnetoresistive effect element includes an oxide non-magnetic film provided on a side opposite to the first non-magnetic layer of the free layer, having satisfactory flatness.
In one embodiment of this invention, a magnetoresistance effect element further includes a pinning layer magnetically coupled to the first oxide magnetic film.
In one embodiment of this invention, the free layer further includes a second metal magnetic film provided on a side opposite to the first metal magnetic film of the first oxide magnetic film.
In one embodiment of this invention, a magnetoresistance effect element includes a pinning layer magnetically coupled to the first pinned layer.
In one embodiment of this invention, the first pinned layer further includes a second metal magnetic film provided on a side opposite to the first metal magnetic film of the first oxide magnetic film.
In one embodiment of this invention, the first pinned layer further includes a second metal magnetic film provided on a side opposite to the first metal magnetic film of the first oxide magnetic film; a third metal magnetic film; and an exchange-coupling non-magnetic film antiferromagnetically exchange-coupling the second and third metal magnetic films.
In one embodiment of this invention, the first pinned layer further includes a non-magnetic film provided on a side opposite to the first metal magnetic film of the first oxide magnetic film; and a second oxide magnetic film magnetically exchange-coupling the first oxide magnetic film via the non-magnetic films.
In one embodiment of this invention, the first oxide magnetic film contains Fe element.
In one embodiment of this invention, the first oxide magnetic film contains Fe and X element where X is at least one element selected from Al, Si, B, and N.
In one embodiment of this invention, the first oxide magnetic film contains MFe2O4 as a major component where M is at least one element selected from Fe, Co, and Ni.
In one embodiment of this invention, the first oxide magnetic film contains Fe3O4 as a major component.
In one embodiment of this invention, the first oxide magnetic film contains CoFe2O4 as a major component. p In one embodiment of this invention, the pinning layer contains Pxe2x80x94Mn where P is at least one element selected from Pt, Ni, Pd, Ir, Rh, Ru, and Cr.
In one embodiment of this invention, the pinning layer contains xcex1-Fe2O3 or NiO or both, or includes an xcex1-Fe2O3 film and a NiO film.
In one embodiment of this invention, the pinning layer includes an (AB)2Ox layer where a ratio of the combination of element A and element B to oxygen is equal to 2:x; 2.8 less than x less than 32; and where t is defined as:
t=(Ra+Ro)/(2xc2x7(Rb+Ro)) 
(where Ra, Rb, and Ro denote the ion radii of the atoms A, B, and O, respectively)
and t satisfies 0.8 less than t less than 0.97.
In one embodiment of this invention, element B of the (AB)zOx layer includes at least one transition metal, and has Fe as a major component.
In one embodiment of this invention, element A of the (AB)aOx layer includes at least one element selected from rare earth metals.
In one embodiment of this invention, the first oxide magnetic film is an oxide of the first metal magnetic film.
In one embodiment of this invention, the first metal magnetic film includes a Coxe2x80x94Fe alloy.
In one embodiment of this invention, the free layer includes a non-magnetic film and two metal magnetic films which are antiferromagnetically exchange-coupled via the non-magnetic film; and the two films have different thicknesses or different levels of saturated magnetization.
In one embodiment of this invention, the magnetoresistance effect element further comprises electrodes provided on the upper and lower sides thereof; and a current flows vertically through the magnetoresistance effect element.
According to another aspect of the present invention, a magnetoresistance effect type head includes the above-described magnetoresistance effect element and a shield.
According to another aspect of the present invention, a magnetoresistance effect type head includes the magnetoresistance effect element; and a yoke for introducing a magnetic field into the magnetoresistive effect element.
According to another aspect of the present invention, a magnetic recording apparatus includes the magnetoresistance effect type head; a servo section for controlling the magnetoresistance effect type head to track a recording medium; and a signal processing section for processing a signal which the magnetoresistance effect type head records or reproduces onto or from the recording medium.
According to another aspect of the present invention, a magnetoresistance effect memory element includes the magnetoresistance effect element; an information reading lead line for reading information from the magnetoresistance effect element; and an information recording lead line for recording the information into the magnetoresistance effect element.
According to another aspect of the present invention, a method for producing the magnetoresistance effect element, includes a first step for forming the first oxide magnetic film via sputtering using an oxide target.
In one embodiment of this invention, the oxide target contains Fe3O4.
In one embodiment of this invention, the first step includes a second step for forming the first oxide magnetic film via sputtering using an inert gas and oxygen gas.
In one embodiment of this invention, the first step includes a second step for forming the first oxide magnetic film via sputtering using an inert gas and oxygen gas.
In one embodiment of this invention, the oxide target contains CoFe2O4.
According to another aspect of the present invention, a method for producing a magnetoresistance effect element, includes a first step for forming a free layer, a non-magnetic layer, and a metal magnetic film of a pinned layer successively directly on a substrate, or via a layer on the substrate; a second step for oxidizing a surface of the metal magnetic film of the pinned layer; a third step for forming an oxide magnetic film on a surface of the metal magnetic film; and a fourth step for forming a pinning layer on the oxide magnetic film. A magnetization direction of the free layer is easily rotated in response to an external magnetic field, and a magnetization direction of the pinned layer is not easily rotated in response to an external magnetic field.
In one embodiment of this invention, the second step includes plasma oxidization.
In one embodiment of this invention, the second step includes a step for oxidizing the surface of the metal magnetic film using oxygen radicals generated by an oxygen radical source.
In one embodiment of this invention, the second step includes natural oxidation.
In one embodiment of this invention, the second step includes a step for oxidizing the surface of the metal magnetic film using oxygen ions generated by an oxygen ion source.
According to another aspect of the present invention, a method for producing a magnetoresistance effect element, includes a first step for forming a free layer, a non-magnetic layer, and a first metal magnetic film of a pinned layer successively directly on a substrate, or via a layer on the substrate; a second step for forming an oxide magnetic film of the pinned layer; a third step for forming a second metal magnetic film on a surface of the oxide magnetic film via reactive sputtering; and a fourth step for forming a pinning layer on the second magnetic film. A magnetization direction of the free layer is easily rotated in response to an external magnetic field, and a magnetization direction of the pinned layer is not easily rotated in response to an external magnetic field.
Thus, the invention described herein makes possible the advantages of (1) providing the magnetoresistance effect element in which the pinned layer includes a multilayer film of the metal magnetic film and the oxide magnetic film, thereby obtaining a high MR ratio and in which the pinning layer is made of Ptxe2x80x94Mn, thereby obtaining thermal stability without losing the high MR ratio; and (2) providing the method for producing the magnetoresistance effect element.
These and other advantages of the present invention will become apparent to those skilled in the art upon reading and understanding the following detailed description with reference to the accompanying figures.